We have a custom issue field of type "Text field (multi-line)" that is supposed to hold urls. This field is filled by an automation rule:
The result looks like this: 
I have tried Jira Markup by enclosing the urls in square bracktes [myurl] as well as HTTP Markup by using <a href="myurl"/>. Neither works. Is there a way to render these URLs as such, so that they are clickable and open the Ressource behind the url?